Integrated circuit (IC) technologies are constantly being improved. Such improvements frequently involve scaling down device geometries to achieve lower fabrication costs, higher device integration density, higher speeds, and better performance. Photolithography is frequently used for forming components of an integrated circuit device. Generally, an exposure tool passes light through a photomask or reticle and focuses the light onto a photoresist layer of a wafer, resulting in the photoresist layer having an image of integrated circuit components therein. Printing device patterns with small spacings is limited by a minimum pitch printing resolution of the exposure tool. Multiple patterning technology (MPT) has thus been implemented to improve pattern resolution as device densities increase. MPT separates a pattern layout into more than one mask, essentially assigning features of the pattern layout to several masks. The masks associated with the pattern layout are then used to transfer the pattern layout to a wafer, thereby pushing photolithography's limits.
To achieve pattern layouts that are MPT compliant, an exemplary MPT method assigns each feature of the pattern layout either a first color or a second color based on various MPT rules. Features assigned the first color are formed on a first mask, and features assigned the second color are formed on a second mask. Each mask is then used in a photolithography process to transfer the features assigned on the first mask and the second mask to a wafer, such that the wafer includes the pattern layout. It has been observed that when portions of the pattern layout that are associated with a given device are split into more than one mask, and thus, more than one lithography step, routing and device characteristic variations may occur. This can lead to device performance degradation. Accordingly, although existing multiple patterning technology methods have been generally adequate for their intended purposes, as device scaling down continues, they have not been entirely satisfactory in all respects.